Properties of asymmetric high critical temperature dc SQUIDs

Asymmetries between the two Josephson junctions of a de-SQUID have always b een considered undesirable spurious effects, responsible for the degradatio n of the device performance. However, it was recently demonstrated that a suitable choice of the asymmet ric configuration can lead to magnetic flux noise values lower than symmetr ic ones, The numerical analysis was performed by using parameters typical o f low-Tc SQUIDs, operating at the liquid helium temperature. In this paper,the analysis has been extended to high critical temperature d e SQUIDs, operating at the liquid nitrogen temperature. Also in this case, asymmetric SQUIDs show the best performance in terms of both flux to voltag e transfer coefficient V-phi and magnetic flux noise S-phi. In order to opt imize the device performance, the dependence of SQUID properties on damping resistance and normalized SQUID inductance has been computed for both symm etric and asymmetric configurations.